When t/stat turns on with setting of 78deg inducer motor & blower kicks on then igintor kicks on then burner kicks on after little while burner turn-off then blower speed gets low , inducer motor still runs,green light blink with 3 times & hold again blink 3times,then inducer motor turns off, again doing the same cycle,temperature not rise more than 67deg,I am refrigeration tech,pls. give me some clue or hints to work on with,thanks
Sounds like its tripping a limit switch or if it has a flame rod .you may need to clean it. Possibly tripping the high limit due to dirty filter. usually has a diagnostic sheet on one of the panels that will tell you what is going on check the panel you see the light closest to.
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Induced fan motors on older units are wired through the high limit safety on the stack - in series. When the furnace calls for heat, the induced fan motor comes on and after a time the furnace will light.
Older units have a temp switch in the stack that rotates to bring on the burners and blower motor. . When there is a call for heat, the induced draft fan motor comes on and then the burners will light.
After the heat exchanger is warmed up the limit switch will bring the blower motor on. That's basically how it works - there are two circuits - one for the induced draft motor and the burners and the other for the blower and high limit.
New units have a plug on the board you just plug in.
power to gas valve ok .. Replace gas valve after checking gas valve coil for continuity/resistance... with valve removed ...and power to valve ... try blowing thru valve from supply side ... stuck valve.... replace...
This is the proper cycle of a furnace and what should happen.
Inducer motor kicks on, it runs for a little bit, about 3-5 seconds, then you should see a bright yellow glow, this is the igniter, shortly after, you should hear a click and the gas should start to flow, almost immediately it turns to a blue flame. Then your igniter should turn off and the blower motor start up.
If the pilot turns on and the gas ignites, then shortly after the unit shuts off, chances are this is your blower motor. It is not starting up, then the heat limit is reached in your unit and the safety shuts it off.
Sounds like a faulty board. shut the power to the furnace off for a minute then turn it back on. Make a call for heat at the thermostat. The inducer should start and close contacts on a pressure switch . Once pressure switch closes the hot surface ignitor should glow red. Then the gas valve will open when the gas valve opens you should get fire till the stat is satisfied. If your concerned it is the jump out r to w on the board this will eliminate the stat. If you to reset the rollout switchs 3 timesyou're getting flame rollout and you either have a cracked heat exchanger or blockage in the exhaust piping or a bad inducer motor. Keep me posted with what you find!
First make sure that your thermostat is turned to heat and auto settings. Then turn up t-stat to where it should be calling for heat.If nothing happens then make sure you have power to heater, gas valve is turned on and blower compartment door is securely latched. If still nothing turn t-stat to fan on and the blower should come on and run until you shut it off. If it does this then you know that you have power to furnace and that the blower works.After you are sure that you have power then remove thermostat cover from base. If stat wires are connected to front of base then disconnect red and white wires and temporairly touch them together. This should send power to your furnace and start the ingnition cycle. If this works then replace thermostat. The sequence of events in the ignition cycle are t-stat calls for heat, induced draft motor comes on and runs for about 20 seconds,then ignitor comes on and lights pilot,then burner lights for 1-2 mins and then blower comes on. I would start at the t-stst and work my way through it. If I can be of any help please ask. Thank you
When the furnace first comes on there is a induced draft motor that should come on first but that forces air up the exhaust or flue,not into supply air on ductwork. It is not unusual for cold air to be blown out when burner first turns blower motor on. This should last for a short period of time, no more than a min. or two. You can watch furnace cycle by removing top front cover, I should back up here and ask is this a gas or electric unit. If it is gas you should be able to watch burner flames for a short time before blower comes on. I really need more information so I can try to ascertain what is going on. Wish I could be more help. Thank you.
When a furnace is replaced with a newer style unit like yours with an inducer motor, they sometimes use the old vent pipe. These old style vent pipes are transite (light weight cement), the moisture created from your furnace exhaust is caught on the cool transite surface and runs back down into the blower blades or wheel bringing a white mineral deposit with it which causes your problem. The vent should nave been replaced with the heater using a metal vent material. You will need to replace your inducer motor assembly and vent pipe to prevent a recurrence.
be sure the fan setting on the stat is set for auto, not on. in this mode the fan should only run when there is a call for cool or heat.if the fan continues to run check at the control board to see if you are getting 24 volts low voltage between green and common. if you are then the stat is bad. if youaren't then your electric control board is possibly bad. a lot of gas furnaces fall into a failsafe mode when a sensor or function fails and the blowers stay on 24 7. you may well have several problems from what you are saying. if you turn everthing off and start a new cycle for heat the first thing that should fire up is the induced draft motor , then the ignotor, then the gas valve. you can check each item with a meter , generally 120 volts to the induced draft motor, then 120 volts to the ignitior, the 24 volts to the gas valve. then ignition and 120 volts to the motor. most furnaces have a heat terminal and a cool terminal on the board. common to heat should get 120 volts on a call for heat after the sequence of operationb has taken place. 120 volts should be sent to cool terminal on a call for cool. a continueous blower is a sign of a failed safety. perhaps the motor failed and the safety opened and the motor was replaced but the safety never reset?. look at all the little micro temp sensors around the burner. they are like little breakers and need to be pushed in to reset . usually like a little stem that pops out from a metal or plastic dic. some are size of a quarter, some the size of a dime.
most forced draft fans are powered by 120 volts . close to the fan is usually a plug that unsnaps. create a call for heat after turning off to clear safetys and see if your getting 120 to fan on initial call for heat. if you are then fan draft motor is bad, usually sold as an entire assembly replace exact as it came out. sequence of operation is..... stat calls for heat via common and white wire to furnace , 24 volts. ......board sences call and sends 120 volts to forced draft ........ motor runs and creates pressure on proofing switch,....... switch closes 24 to board and tells it draft fan is on......... board then energizes ignitor,....... after ignitior glows gas valve is opened and burner lights ........ either ignitor or seperate sensor rod tells board the burner lit........ and a few minutes later the fan comes on and hot air is blown out. if a step is missed or doesn't proof the furnace either trys up to three times to light or locks out. turning off power usually resets safetys and it will resume attempts to lite normally.